Nucleic acids such as siRNA and DNAzymes have been contemplated as active ingredients in therapeutic strategies. DNAzymes are short deoxyribonucleotide sequences that cleave target RNA sequences, e.g., mRNA. Small interfering RNA (siRNA) contains RNA sequences which are typically between 20-25 nucleotides in length. siRNA interferes with the expression of a specific gene containing the siRNA sequences. DNAzymes hold potential advantages over siRNA for therapeutic gene regulation due to their innate ability to catalytically cleave mRNA without the need for hijacking the RISC (RNA-induced Silencing Complex) machinery of the cell.
DNAzymes targeting mRNA of integrins reduced protein expression in endothelial cells and thus blocked microvascular endothelial cell capillary tube formation. See e.g., Niewiarowska et al., Cancer Gene Ther. 2009, 16(9):713-22. DNAzyme regulation of the EGFR gene expression levels was shown to inhibit the growth of cancer cells. See Santiago et al., Nature Med. 1999, 5:1264-9. DNAzymes that cleave VEGFR2 mRNA were shown to limit the proliferation of endothelial cells and blocked tumor growth in vivo. Zhang et al., Cancer Res. 2002, 62:5463-9.
The movement of nucleic acids to a site of interest within a cell presents a challenge to using nucleic acids as therapeutic agents. Cell membranes generally prevent nucleic acids from migrating in and out of cellular compartments. Cationic polymers or liposomes may be employed to improve delivery. Cationic liposomes are toxic to cells. Once within the cells, biological processes degrade oligonucleotides. Chemically modifying the oligonucleotide backbone can slow nuclease activity. In any case, there is exists a need to identify improved compositions and methods.
Liu & Lu disclose a gold nanoparticle/DNAzyme assembly for a biosensor application. See Chem. Mater., 2004, 16, 3231-3238. See also Yang et al., Chem Commun, 2010, 46, 3107-3109. Rosi et al., disclose oligonucleotide-modified gold nanoparticles for intracellular gene regulation. See Science 2006, 312, 1027. Giljohann et al., disclose gene regulation with polyvalent siRNA-nanoparticle conjugates. See J. Am. Chem. Soc. 2009, 131, 2072. See also Hurst et al., Anal. Chem., 2006, 78 (24):8313-8318 and Liu et al., Analyst, 2012, 137, 70-72. References cited herein are not an admission of prior art.